This invention relates to medical treatments of objects within anatomical lumens of the body, and more specifically, to devices and methods for entraining and extracting such objects from within the body.
Concretions can develop in certain parts of the body, such as in the kidneys, pancreas, and gallbladder. Minimally invasive medical procedures generally involve causing limited trauma to the tissues of a patient, and can be used to dispose of problematic concretions. Lithotripsy and ureteroscopy, for example, are used to treat urinary calculi (e.g., kidney stones) in the ureter of patients.
Lithotripsy is a medical procedure that uses energy in various forms such as acoustic shock waves, pneumatic pulsation, electrical hydraulic shock waves, or laser beams to break up biological concretions such as urinary calculi (e.g., kidney stones). The force of the energy, when applied either extracorporeally or intracorporeally, usually in focused and continuous or successive bursts, comminutes a kidney stone into smaller fragments that may be extracted from the body or allowed to pass through urination. With the help of imaging tools such as transureteroscopic video technology and fluoroscopic imaging, the operator of the lithotripter device can monitor the progress of the medical procedure and terminate treatment when residual fragments are small enough to be voided or removed.
Intracorporeal fragmentation of urinary calculi can prove problematic in that stones and/or stone fragments in the ureter may become repositioned closer to and possibly migrate back toward the kidney, thereby requiring further medical intervention to prevent the aggravation of the patient""s condition. It is desirable to be able to extract such fragments from the body using a single instrument, to prevent the need for successive instrumentation.
Many known stone extraction devices are rigid and lack the maneuverability and flexibility to engage and disengage repeatedly a stone without harming the surrounding tissue. For example, if a stone is still too large to be extracted without further fragmentation, it can be difficult to disengage the stone from such an extraction device without damaging the delicate lining of the ureteral wall.
The present invention mitigates the risk of damage to surrounding body tissue when treating and/or removing organic material (e.g., blood clots, tissue, and biological concretions such as urinary, biliary, and pancreatic stones) and inorganic material (e.g., components of a medical device or other foreign matter), which may obstruct or otherwise be present within the body""s anatomical lumens. In one embodiment, the invention prevents the upward migration of stone fragments generated during a stone fragmentation procedure and safely and efficiently extracts fragments from the body. The invention also enables repeated application to stones, stone fragments, and other biological and nonbiological/foreign material while minimizing trauma to the surrounding tissue.
A medical device, in accordance with an embodiment of the invention, comprises a core element made at least partially of a shape-memory material. Shape-memory material is a material that can be formed into a particular shape, retain that shape during resting conditions (e.g., when the shaped material is in free space or when external forces applied to the shaped material are insufficient to substantially deform the shape), be deformed into a second shape upon subjecting the initial shape to a sufficiently strong external force, and revert substantially back to the initial shape once the external force is no longer applied. Examples of shape memory material includesynthetic plastics, stainless steel, and superelastic, metallic alloys of nickel/titanium (commonly referred to as nitinol), copper, cobalt, vanadium, chromium, iron, or the like. In one embodiment, a first portion of the core element extends substantially longitudinally, and a second portion is wound to form a helical coil. The helical coil is adapted to taper from a larger diameter at a proximal end thereof to a smaller diameter at a distal end thereof, thereby resembling a helical cone shape.
In one embodiment, a flat wire (with, for example, a square, rectangular, or other quadrilateral cross-section) substantially wraps the first and second portions of the core element. A distal end of the flat wire can be attached to the distal end of the helical coil, so as to maintain the relative orientation and position between the flat wire and the core element. In a further embodiment, a layer of polymeric material substantially covers the entire outer surface of the flat wire (i.e., the surface of the flat wire that contacts the walls of the anatomical lumen or catheter), including that portion of the flat wire that wraps both the first and second portions of the core element. In another embodiment, the polymeric layer covers a portion of the outer surface of the flat wire wrapping the second portion of the core element, while leaving the outer surface of the flat wire wrapping the first longitudinal portion of the core element uncovered. Alternatively, the polymeric layer covers the outer surface of the flat wire wrapped about the second portion of the core element and at least a portion of the first longitudinal section in the vicinity of the helical cone.
In another embodiment, a wire element substantially wraps only the first longitudinal portion of the core element, and a sheath (of, for example, a polymeric material) covers the second, helical cone portion of the core element. The proximal end of the sheath can be attached to the distal end of the wire element, and the distal end of the sheath can be attached to the distal end of the second portion of the core element.
In yet another embodiment, the curved, second portion of the core element is covered substantially by a polymeric material and the longitudinal section of the core element remains uncovered. In this embodiment, the core element is not covered by a wire element.
In one embodiment, the polymeric material/layer is applied by spraying. For example, a polymeric material can be spray-coated onto the outer surface of the wire and/or directly onto the helical cone section of the core element. In another embodiment, the polymeric material can be a sheath that is heat-shrunk about the wire and/or the second portion of the core element. The polymeric sheath can be made of PTFE, EPTFE, ETFE or other suitable material that exhibits a light color capable of reflecting most of the laser energy used during a lithotripsy procedure and absorbing or dissipating the energy not reflected with no or minimal damage to the polymeric sheath at normal laser operating levels.
The polymeric sheath preferably comprises a plurality of colors along a length of the sheath in order to assist the physician who is performing the lithotripsy procedure to detect movement in the sheath and to assist in gauging distances. In this manner, the physician can determine not only when the second portion of the core element (corresponding to the curved or helical cone section of the core element) is deployed/expanded, but also the configuration of the core element during various phases of the lithotripsy procedure. In one embodiment, the polymeric sheath exhibits the standard color of a PTFE heat shrink extrusion with a colored stripe along the length of the sheath. As the medical device is manipulated, the relative size and distances of the wound sections of the helical coil can be readily determined by examining the spiral configuration of the colored stripe, which appears about the wound section of the core element. The striped color is also preferably selected to be resistant to and reflect laser energy so as to minimize damage to the polymeric sheath.
The helical cone is adapted to ensnare objects of various sizes from within an anatomical lumen, e.g., a kidney stone from within a ureter. Superelastic properties of the helical cone can enable it to unwind and assume a substantially linear configuration upon being subjected to a pulling force along a longitudinal axis of the core element, such as when the helical cone is pulled within a catheter adapted to receive the core element, the wire, and the polymeric sheath. The cone can be pulled into an outer catheter when a captured stone or other object is too large to pass through the anatomical lumen without further fragmentation or other treatment. The helical cone substantially rewinds into its helical cone rest state when released and unrestrained by such a force.
The substantially linear configuration of the helical cone when positioned within the catheter enables the catheter to retain a small diameter, which facilitates the placement of the catheter beyond the object in the anatomical lumen. Once the catheter is properly positioned, the second portion of the core element is pushed out of the distal end of the catheter where the helical cone substantially rewinds or expands back into its tapered configuration. As discussed, the helical cone can be reversibly transformed into a substantially linear configuration when drawn into the catheter so that it can be repeatably positioned and deployed in more advantageous locations.
In yet another aspect, the second portion of the core element forms one or more curved shapes in addition to the helical cone, such as another helical cone or a single loop. The single loop or curved element can be located near the proximal end of the helical cone in order to assist in the manipulation, extraction, or repositioning of the kidney stone or other object in the anatomical lumen. The second helical cone can be located near the distal end of the first helical cone so that if the first helical cone unwinds and is pulled into the catheter when a kidney stone or other object is too large to pass through the anatomical lumen, the second helical cone can serve as a backstop during the subsequent treatment procedure without having to redeploy the first helical cone.
Regardless of the particular curved element employed, the curved element can be made of or include superelastic/shape-memory material that enables the deformation and reformation of the curved element as described above in connection with the helical cone. Similarly, the curved element can be wrapped entirely by a wire element, such as round or flat wire, or can be covered by a polymeric material as described above in connection with the helical cone. Those skilled in the art will recognize that the various wire wrapping and polymeric covering embodiments previously discussed in connection with the helical cone can be used as well for the curved element. The wire wrapping and polymeric covering techniques can also be common or different as between the curved element and the helical cone. For example, the first longitudinal portion of the core element can be wrapped in flat wire, while the curved element and helical cone are covered by a polymeric sheath. Alternatively, the first longitudinal portion of the core element can be uncovered, while the shaped portion(s) of the core element are covered with a polymeric sheath, which can comprise a plurality of laser resistant colors.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.